Why are you trying to purge the slips? Generally you run bills and the slips are marked approved and you leave them in the database. Especially with the new platform there's no need to purge slips.
Are the AR balances correct? When you look at the slips in the slip list do they have a yellow or red envelope next to them?

Thanks for your response. Yes, balances are correct. There is a yellow envelope next to each slip and each slip says "billed." However, the status says "billable." Is all of this correct? Thanks in advance, Mark

Billed and Billable are different. When you create a slip it is Billable, No Charge or Do Not Bill. It retains this status permanently. Billed means it was included on a bill. The yellow envelope and the Billed status mean it was billed. Sounds like everything is correct. Again you don't need to purge the slips. Since they are billed, they will not show up on another bill. If you purge them you lose the ability to create slip based reports.

What a thorough answer! Thanks again. Sounds like everything is working OK. BTW, I was a certified consultant many years ago when I first purchased Version 8! Always a challenge to get new clients. But, I really appreciate your help. Thanks, Mark